Question

Baking soda is an example of pure substance because:
(A) The constituent particles have constant composition.
(B) It has consistent property throughout the mixture.
(C) Both a and b
(D) None of these.

Answer 1

Hint: A pure substance consists of a single kind of molecule. It always has a constant composition and the same set of properties. Also, its constituent elements cannot be separated by physical methods.

Complete Solution :
Baking soda is a chemical compound known as sodium bicarbonate and has the chemical formula - $$NaHC{O}_3$$. A sample of pure baking soda consists of 57.1% sodium ($$Na$$), 1.2% hydrogen ($$H$$), 14.3% carbon ($$C$$) and 27.4% oxygen ($$O$$). If we heat the sample at a temperature of $$270{}^{\circ }\text{C}$$, the sample will decompose. It will give off carbon dioxide and water vapour and will leave behind a residue of sodium carbonate. Therefore, we can say that baking soda is a pure substance as it has a constant composition and unique set of properties.
 So, the correct answer is “Option C”.

Additional Information : - The IUPAC name of baking soda is sodium hydrogen carbonate.
- Intake of too much baking soda leads to vomiting and diarrhea as our body tries to correct the high sodium concentration by pulling more water into the digestive tract. Also, after absorption, high sodium concentrations can cause dehydration, kidney failure and seizures.

Note: We should not get confused in the words ‘Baking soda’ and Bicarb soda’ as both means the same thing. We should also keep in mind that Baking Powder and Baking soda are two different things. We can substitute baking powder in place of baking soda but we can’t use baking soda when a recipe calls for baking powder.